C#怎么实现文件下载功能的四种方法

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    //TransmitFile实现下载
    protected void Button1_Click(object sender, EventArgs e)
    {
        /*
         微软为Response对象提供了一个新的方法TransmitFile来解决使用Response.BinaryWrite
         下载超过400mb的文件时导致Aspnet_wp.exe进程回收而无法成功下载的问题。
         代码如下：
         */

        Response.ContentType = "application/x-zip-compressed";
        string FileName = "test.doc";
        //使用UTF-8对文件名进行编码
        Response.AppendHeader("Content-Disposition", "attachment;filename=\"" + HttpUtility.UrlEncode(FileName, System.Text.Encoding.UTF8) + "\"");
        Response.ContentType = "application/octet-stream";
        Response.AddHeader("Content-Disposition", "attachment;filename=" + FileName);
        string filename = Server.MapPath("../ReportTemplate/test.doc");
        Response.TransmitFile(filename);
    }

    //WriteFile实现下载
    protected void Button2_Click(object sender, EventArgs e)
    {
         /*
         using System.IO;
         */
        string fileName = "test.doc";//客户端保存的文件名
        string filePath = Server.MapPath("../ReportTemplate/test.doc");//路径
        FileInfo fileInfo = new FileInfo(filePath);
        Response.Clear();
        Response.ClearContent();
        Response.ClearHeaders();
        Response.AddHeader("Content-Disposition", "attachment;filename=\"" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8) + "\"");
        Response.AddHeader("Content-Length", fileInfo.Length.ToString());
        Response.AddHeader("Content-Transfer-Encoding", "binary");
        Response.ContentType = "application/octet-stream";
        Response.WriteFile(fileInfo.FullName);
        Response.Flush();
        Response.End();
    }

    //WriteFile分块下载
    protected void Button3_Click(object sender, EventArgs e)
    {
        string fileName = "test.doc";//客户端保存的文件名
        string filePath = Server.MapPath("../ReportTemplate/test.doc");//路径


        System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);


        if (fileInfo.Exists == true)
        {
            const long ChunkSize = 102400; //100K 每次读取文件，只读取100K，这样可以缓解服务器的压力
            byte[] buffer = new byte[ChunkSize];


            Response.Clear();
            System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
            long dataLengthToRead = iStream.Length; //获取下载的文件总大小
            Response.ContentType = "application/octet-stream";
            Response.AddHeader("Content-Disposition",
                "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
            while (dataLengthToRead > 0 && Response.IsClientConnected)
            {
                int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize)); //读取的大小
                Response.OutputStream.Write(buffer, 0, lengthRead);
                Response.Flush();
                dataLengthToRead = dataLengthToRead - lengthRead;
            }
            Response.Close();
        }
    }

    //流方式下载
    protected void Button4_Click(object sender, EventArgs e)
    {
        string fileName = "test.doc";//客户端保存的文件名
        string filePath = Server.MapPath("../ReportTemplate/test.doc");//路径

        //以字符流的形式下载文件
        FileStream fs = new FileStream(filePath, FileMode.Open);
        byte[] bytes = new byte[(int)fs.Length];
        fs.Read(bytes, 0, bytes.Length);
        fs.Close();
        Response.ContentType = "application/octet-stream";
        //通知浏览器下载文件而不是打开
        Response.AddHeader("Content-Disposition", "attachment;  filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
        Response.BinaryWrite(bytes);
        Response.Flush();
        Response.End();
    }
}